A 114 bp fragment of the human papillomavirus type 16 (HPV16) E2 open
reading frame (nt. 3142-3255) containing a putative estrogen responsiv
e element (ERE) was amplified and cloned into pBLCAT2 plasmid in both
sense (p159-4) and anti-sense (p164) orientation. The plasmids were tr
ansfected into human breast-cancer cell line MCF-7 containing estrogen
receptor and the cultures were kept in the presence of absence of bet
a-estradiol. The chloramphenicol acetyltransferase (CAT) activity was
not influenced by estrogen. However, a silencer effect was observed bo
th in cultures transfected with p159-4 and p164 plasmids. We prepared
and cloned synthetic fragments containing the putative ERE and failed
to prove that the palindrome in the putative ERE was responsible for t
he silencer activity.